The long run is the cornerstone of marathon training, yet it trips up many runners. You may be one of them: Once you start amping up the volume, your body starts shutting down. Another 26.2 dream dashed. Or is it? According to Brian MacKenzie, a power lifter turned ultraendurance athlete based in southern California, to go long, you have to be strong. To that end, MacKenzie, along with partner and two-time California state cycling champion Doug Katona, created CrossFit Endurance (CFE), a high-intensity, low-volume training plan that blends CrossFit conditioning (i.e., heavy, explosive strength training) with sprints, time trials, and tempo workouts. Goodbye, long runs. CFE reduces mileage to as much as one-quarter the average of a typical marathon program.

MacKenzie developed CFE while training for Ironman and ultramarathon events. Following long, slow distance (LSD) training while preparing for an Ironman in 2004, he experienced knee problems and plantar fasciitis. So he did something radical. He replaced LSD workouts and easy runs with 20-minute Cross-Fit workouts, a conditioning program developed by former gymnast Greg Glassman that takes functional training to the extreme by combining power lifting, gymnastics, kettlebell training, and other blisteringly hard strength training. He kept the high-intensity speedwork found in many 26.2 plans, like 400-and 800-meter repeats. It worked for him—his high-test training twist helped MacKenzie evade injury and finish ultramarathons on less than 10 hours of training a week. In 2007, he launched CFE and remains vehement that a strong—really strong—body will carry you as far as you want to go.

Some experts are concerned that forfeiting the long run does not adequately prepare marathoners—especially newcomers—to the rigors of extended time on their feet. However, even the most skeptical scientists acknowledge there's wisdom behind CFE and that—like most plans—it may work for some runners.

Build your base—faster

Runners spend a lot of time talking about "base," the aerobic fitness foundation—characterized in part by a stronger heart muscle, thicker capillary webbing, and improved enzyme production—necessary for optimum endurance performance. Traditionally, you've been told the best way to build your base is with long, slow aerobic workouts.

Yet some experts argue such adaptations can occur in less time with high-intensity runs. "If you do 400-meter repeats, the vast majority of energy is coming from aerobic metabolism, making sprints a very potent aerobic stimulus," says Martin Gibala, Ph.D., professor of kinesiology at McMaster University in Hamilton, Ontario. Gibala and his colleagues found that people who did short (25 minutes) cycling workouts with a series of 30-second sprints improved their fitness over two weeks at the same rate as those who rode for two hours at a lesser intensity. "Pretty much every adaptation we measured could be realized through high-intensity interval training (HIIT) and lower volume."

Gibala acknowledges that his study reflects a short period of training. "What we don't know is how this plays out long term," he says. "If you have 50 runners doing traditional training and 50 doing HIIT training for one full year, who turns out better trained? We haven't done that study. But I bet they're close."

Build a really strong body

The other half of MacKenzie's program is building strength through CrossFit. Workouts average 10 to 20 minutes, and combine "metabolic conditioning" exercises such as kettlebell swings, handstand push-ups, and pull-ups with classic moves like deadlifts and squats.

All that heavy lifting can translate to distance running. For one, it increases the force of your stride—the more powerful your push-off, the less effort you exert with each stride, the easier fast running feels, says Stephen S. Cheung, Ph.D., professor of kinesiology at Brock University in Ontario. "It also makes you more balanced and likely less prone to injury," he says.

It may also make you faster. In one study, highly trained runners who substituted almost a third of their running workouts with explosive, sport-specific strength training shaved 30 to 40 seconds off their 5-K times after nine weeks compared with those who ran and did minimal strength training.

Put it together

For runners, a typical CFE workout week might look like this: three double days—a strength-building session followed several hours later (to allow for recovery) by a short, high-intensity run; one or two days of longer endurance workouts like a tempo run or time trial; and one day of rest.

There are no easy days or recovery runs in CFE. You're either on or you're off. "The act of taking real rest might be enough to help many runners improve performance," says Gibala. "You have runners going out for these recovery runs, but they're just making themselves tired. You're better off reducing the total training load, getting rid of the junk, and getting real rest."

Is it for you?

If you're a longtime athlete who's feeling worn down, a program like CFE could be just what you need, says James Herrera, M.S., C.S.C.S., owner of Performance Driven coaching and consulting in Colorado Springs. "Most runners have trained in the classic format for many years and have developed a huge volume base," he says. "If you drastically reduce volume and increase strength and training intensity, such an athlete will improve on many fronts: speed, power, economy of movement, lean body mass, as well as confidence. I've taken 40-to 60-year-old clients who've done endurance training for 20-plus years, cut their volume in half—still more volume than what CFE prescribes—while increasing intensity, and they've all posted PRs, some better than their 25-and 30-year-old times."

What's less clear is how well the program works for less-seasoned runners, particularly those gunning for marathon (and beyond) distances. CFE proclaims that by following the program to the letter, you can compete in—not just complete—ultra and Ironman distances on just six to eight hours of training per week. That includes "long" runs that never exceed 90 minutes. But if you've never done a really long run, race day could prove challenging, says Herrera, an ultrarunner himself.

"[Long runs] prepare you for time on your feet, pacing for the long haul, mental toughness, and, most important, how to hydrate and feed yourself for multiple hours—you don't really need to eat for a 90-minute training session," he says. "I'm a firm believer in HIIT, but I still feel a runner—especially a new runner—has to cover about 75 percent of the distance in training for a marathon to prepare for those elements."

What is certain is that most runners can benefit from some components of CFE—after all, who doesn't want stronger glutes, more stable hips, and faster times? And with the dark days of winter upon us, now is the perfect time to hit the gym and try something fresh. Who knows? You might find a new religion.

MONSTER MOVES

Mix and match three to four of the following CrossFit exercises once a week to boost your strength and endurance

Stand with feet beneath a barbell, shins almost touching the bar, feet under hips. Keeping back straight and chest up, sit back into hips and grip the bar. Take a deep breath in and hold it as you push hips forward, keep arms straight, and lift the bar so it travels a vertical path along your body. Do one set of five to 10 reps.

BUILD ON IT: Increase weight over time until you reach a max weight you can lift two or three times for one set. Progress to three sets, aiming for five reps, three reps, then one rep of max.

Butterfly Sit-Ups

TARGETS: Abdominals

PURPOSE: Challenges abs through a full range of motion

Sit on the floor, knees bent with soles of feet together and toes touching baseboard of a wall. Place a folded towel on the floor behind you, positioned under your lumbar spine when you lie back. Extend arms straight so fingertips touch the wall and, keeping your back straight, lie back until your shoulder blades touch the ground. Sit back up immediately and touch your fingertips to the wall. Repeat 10 to 20 times.

BUILD ON IT: Aim for 50.

Double Unders

TARGETS: Cardiovascular system, calves, hamstrings, glutes, quads

PURPOSE: Builds speed, agility, coordination, balance, and endurance

Jump rope—keep your head up, eyes forward, elbows close to the body, and let your wrists drive the rope around. Jump just high enough to allow the rope to pass under your feet. Land softly on the balls of your feet. Then swing the rope a little faster so it passes under your feet two times per jump. Aim to do 20 jumps without getting tangled.

Sit on floor between two raised platforms; keep legs straight and together. Place a hand on top of each platform. Extend arms and lift body off the floor while bringing knees toward chest. Hold for 10 seconds.

BUILD ON IT: Work up to 30 seconds. As you get stronger, extend one leg. Hold for 15 seconds, then switch legs. Graduate to holding position with both legs straight.

Hold a kettlebell with both hands, arms straight, feet 30 inches apart. With back straight and a slight bend in knees, press hips back and swing the kettlebell between legs and behind hips. Stand up and use hips to drive kettlebell forward and swing the weight over your head. Do 10 to 15.

BUILD ON IT: Work up to 50.

Box Jumps

TARGETS: Quads, hamstrings, glutes

PURPOSE: Increases explosive strength and stamina

Stand in front of a stable platform about 12 to 18 inches high. Push hips back while swinging your arms back. In one explosive move, swing your arms forward, spring up, and land on the box with soft knees. Hop down. Repeat up to 10 times.

BUILD ON IT: Work up to 50 and/or increase platform height.

Kipping Pull-Ups

TARGETS: Core, back, chest, shoulders, biceps

PURPOSE: Turns pull-ups into a full-body, functional exercise

Consider the Kipping Pull-Up to be your aspirational CrossFit exercise—it's a challenging move that takes time and practice to master (and bestows significant bragging rights once you do). Hang from a chin-up bar with your hands about shoulder-width apart, using an overhand grip with your palms facing out. Snap your hips to start swinging your body. When you have enough momentum, bend your knees and pull your torso up until your chin clears the bar. Continue in a fluid manner. Do as many as you can.

BUILD ON IT: Every week add one rep. Or two to four if you've finally nailed it.

RUN ITHigh-intensity short-interval runs build your top-end tolerance, while longer tempo runs and time trials improve aerobic endurance. Perform these workouts at the fastest pace you can sustain for the given effort.

HIGH-INTENSITY INTERVALS

Warm up, then do 8 x 200-meter intervals. Rest (no walking or jogging) 1:30 between each. Maintain pace for each repeat within 3 to 5 seconds. Work up to 5 x 800.

Warm up, then run 1:30 hard followed by 1 minute easy. Repeat 6 to 8 times.

Warm up, then run 1 mile hard. Rest for 5 minutes, then perform 2 to 4 x 600 meters with 1:30 rest between repeats. Run each 600 within 2 to 3 seconds of each other.